Express your answer as a mixed number simplified to lowest terms. $18\dfrac{6}{8}-10\dfrac{2}{5} = {?}$
Answer: Separate the whole numbers from the fractional parts: $= {18} + {\dfrac{6}{8}} - {10} - {\dfrac{2}{5}}$ Bring the whole numbers together and the fractions together: $= {18} - {10} + {\dfrac{6}{8}} - {\dfrac{2}{5}}$ Subtract the whole numbers: $=8 + {\dfrac{6}{8}} - {\dfrac{2}{5}}$ Simplify each fraction: $= 8 + {\dfrac{3}{4}} - {\dfrac{2}{5}}$ Find a common denominator for the fractions: $= 8+\dfrac{15}{20}-\dfrac{8}{20}$ Subtract the fractions: $= 8+\dfrac{7}{20}$ Combine the whole and fractional parts into a mixed number: $= 8\dfrac{7}{20}$